One of the things I really like about the weight machines I use is that there is a little picture that shows me exactly what muscles I am working on. Unfortunately, the cardio machines do not have any such pictures and I was unsatisfied by the vague terminology of "legs." So, prompted by that and my poll (see right), I decided to investigate exactly which muscles are getting a work out when you get on one of these cardio machines. I'm sticking with the main three, the elliptical, the treadmill and the bike just to keep it simple.
Elliptical (it goes first because it's my favorite)
Hamstrings**An incline or going in reverse will put more emphasis on these muscles.
Quadriceps **Apparently you're unlikely to feel the strain on these muscles because the elliptical equally effects all the muscles involved, meaning, all the other muscles are sharing the load, so you will not feel the effects as much.
Gluteus Maximus **Apparently your behind is actively involved in hip extension...it's even more effective when the machine is on an incline (my regular elliptical does not have this, but I'm definitely going to investigate the different ones now).
Triceps and Chest**These muscles are worked when you use the upper body levers provided.
Biceps and Back**Again, muscles are worked when using the upper body levers. Also more emphasis is placed on the muscles when going in reverse.
Deep Core Muscles**If you do not use the levers or hold onto the machine, these muscles will get a workout.
Gluteals **Includes the gluteus maximus, medius, and minimus (who knew there were three?) Every time your moves backwards, your butt gets a workout.
Hip Flexors **Gets worked when the thigh moves upward.
Quadriceps **Gets worked every time you move your thigh up and extend your lower leg.
Hamstrings **The complete opposite of the quadriceps...the get worked when the thigh moves backwards, and your lower leg moves upward.
Calves **Every time you flew your foot downwards, your calf muscles get a workout.
Tibilais Anterior **Aka, your tibia. Every time you flex your foot upwards, this muscles gets a workout.
Abdominals **These muscles contract while you run, helping to keep you balanced.
Quadriceps **These muscles contract on every downstroke and generate much of the force used to puch the pedals.
Hip Extensors **A combination of the gluteus maximus, and hamstrings work to extend the hip and create muscle power to push the pedals.
Hip Flexors **When your leg is lifted at a 90 degree angle (or at the top of the cycling motion) these muscles get a work out.
So there you have it. If you were interested in working on a particular muscle, then hopefully the information above was helpful to you. If not, you know more now than you did 5 minutes ago (which is always a a good thing)!
I found all of this information on the Livestrong website: http://www.livestrong.com/ which has a lot of useful articles and resources if you are interested in fitness.
Have a good day!